Recombinant Methioninase as a DNA Demethylation Agent.

This chapter reviews the effect of methionine (MET) restriction, via treatment with recombinant methioninase (rMETase), on DNA methylation of cancer cells. CCRF-CEM human cancer cells were treated with rMETase under subcytotoxic conditions. The rMETase-treated cells contained significantly lower levels of genomic methylated DNA than did untreated control cells. DNA methylation was measured by incorporation of the methyl group of [H]methyl-S-adenosylmethionine into DNA and by methylation-sensitive arbitrarily-primed PCR. DNA hypomethylation effected by rMETase was of similar extent to that effected by treatment of the cells with the DNA methyltransferase inhibitor 5-azacytidine.